The promoting effect of alkali metal and H2O on Mn-MOF derivatives for toluene oxidation: A combined experimental and theoretical investigation

In this work, different alkali metal (Na or K)-doped manganese-based metal–organic framework (Mn-MOF) derivative materials were obtained from Mn-MIL-100 through ex situ posttreatment method, and their catalytic activities were studied by toluene oxidation. A series of characterization results (N2 adsorption–desorption, X-ray absorption spectroscopy, temperature programmed O2 desorption, etc.) showed that Na-doped Mn-MOF derivatives presented larger specific surface area, lower average manganese valence, and better adsorbed oxygen mobility, which displayed higher catalytic activity. Interestingly, both the addition of alkali metal and the introduction of water in the reaction atmosphere promoted the mineralization of toluene, as demonstrated by in situ diffuse reflectance infrared Fourier transform spectroscopy and thermal desorption-gas chromatography-mass spectrometry. Density functional theory calculations further confirmed that alkali metals and H2O were conducive to the adsorption of toluene, benzyl alcohol, benzaldehyde, benzoic acid and O2. This work provides new ideas for developing high-efficiency and water-promotion Mn-based materials for VOC control.